Various processes have been known and utilized in the prior art for the separation of air into its nitrogen and oxygen dominant constituents. Additionally, the use of a single pressure distillation column is known to have been used in the prior art for such separations.
In U.S. Pat. No. 3,214,926 a method for producing liquid oxygen or liquid nitrogen is set forth. However, in the patent it is necessary to have two distillation columns, one at high pressure and another at low pressure in order to extract liquid oxygen.
In U.S. Pat. No. 3,217,502 a system is described which utilizes a single pressure distillation column. The product of this air separation system is liquid nitrogen. Oxygen which is separated out in this system is vented to waste. In this patent, it is the oxygen waste stream which is expanded in order to provide refrigeration for the air separation system.
An air separation unit for the production of oxygen is disclosed in U.S. Pat. No. 3,394,555 wherein the combustion of a separate fuel source such as powdered coal is burned with oxygen or an air-oxygen mixture in which the oxygen is derived from the air separation unit. This combustion process provided power for the compression of helium gas for refrigeration necessary to the cryogenic separation system. Power from such combustion is derived from a magnetohydrodynamic power generator.
U.S. Pat. No. 3,731,495 discloses an air separation system using an air feed compressor which is powered by combustion gases directed through a turbine. The turbine exhaust heats boiler steam to supplement the compressor drive. Electric generation is also considered. In addition, this reference utilizes two separate columns at separate pressures for the recovery of the individual gaseous components of air which are separated.
U.S. Pat. No. 4,224,045 is directed towards a process where oxygen is produced by distillation of liquefied air in a two column unit. A gas turbine, powered in part by a nitrogen product stream, supplies the energy to compress the feed air.
U.S. Pat. No. 4,382,366 is directed to an air separation system for the recovery of pressurized, substantially pure oxygen gas. The system uses a single pressure distillation column and burns a nitrogen-oxygen waste stream to provide power for the air compressor, the oxygen product compressor and electric generation. The distillation column has a split feed to develop reflux and reboil and to provide initial separation of the liquid and vapor components of the column.
The art as representated above has failed to disclose an efficient manner in which to separate oxygen from air with the utilization of the by-products or waste streams in order to recycle energy necessary for compression both of the feed air and the segregated heat pump fluid. In addition, the prior art has failed to minimize capital expenditures in separating air by the utilization of a single pressure distillation column. The solution to problems such as these are the objectives of the present invention.